jointing compound/joint cement

IME interior filler is pretty much the same thing.

Thanks for the fast reply. So any old polyfilla will do then? I have got some of that glass fibre mesh tape to put along the joint, thought I wonder if I should use paper joint tape instead? You see, I can't plaster, so I was hoping to seal the plaster and paper on top. If the mesh stands slightly proud that won't look good; I wonder whether paper tape will fit more flush to the surface?

Thanks.

wallpapering over unplastered PB is false economy - you can't get the paper off again and the wall will probably have to be demolished the next time you want to decorate

Long and bitter experience has taught me that, even though the various compounds all look like white goo, using the right stuff for the right purpose makes a big difference to the speed and quality of the job. There are many types of filler available, and they are all quite different to plaster. Not least because they go off many times more quickly, enabling you to get on with the job, and most of them respond to sanding pretty well, since they are much softer than set plaster. The guide at the Lafarge site is fairly informative:

BTW, whatever you want to do on top of the wall, bung some a couple of coats of sealer on it (which I suspect may not be too different to emulsion). If you're painting, it evens up the absorbancy of the board and filler, and if you're papering, it claims to let you strip later - not tried that...

You usually only joint like that when using taper edge plasterboard. One starts by applying a mesh scrim tape, and then fills the full width of the taper (approx 8" wide) with the jointing compound. Finally sanding off. Square edge boards are normally scrim taped and then skim plastered all over.

Wickes also do it in bags of powder which you mix up as required.

You can get a small bag of dry mix - probably still way more than you need, but it is cheap enough and keeps better.

Its worth using the right stuff since it sands so nicely compared to plaster or filler. Helps make the job look much nicer IME.

No, you just skim over..

I don't bother with tape. Just fill the gaps with Polyfilla or similar, and lightly sand. After a coat of emulsion you can't see the join. Subsequent movement of the joists isn't normally a problem unless they're new.

I think you need to do it properly with tape and jointing compound or else you will suffer cracks appearing.

When I drylined the cupboard under the stairs, made by opeing up the boxed off area at bottom of the stairs, I ran out of proper dry jointing compound (yes I know its only £2 for 5KG bag...) so I user polyfilla + paper tape on one joint, plaster with PVA + paper tape and rather bodgingly decorators caulk and no tape on another, just to see the differences (actually I ran out of dot and daub so bodged using plaster with a generous portion of PVA, which works fine).

Anyway the boards are still up 10 years later, however the pollyfilla one cracked almost as soon as it was dry, I just filled the crack with excess emulsion when painting. The plaster+PVA one is best, but was a bugger to polish flat and sand afterwards and is still visible. The caulk hasn't cracked but is very messy and clearly a bodge. Luckily all of these are not really visible. Mt excuse is my wife wouldn't let me out of the cupboard to by more jointing compound as she knows a little trip to B&Q, Wickes etc to get just one item can take hours due to the distractions of non job in hand related items etc power tools, plumbing tools etc etc

Anyway my advice is buy the proper jointing compound, goes on well, polishes flat easily when damp, when dry sands easily and doesn't absorb paint excessively when painted and doesn't crack. My preference is the British Gypsum ready mixed stuff, about £11 for 5L, wonderful stuff to work with, great also for filling dents/damage in plasterboard and treating like ready mix pollyfilla and doesn't appear to "go off" like the dry jointing stuff after a year or two. The dry mix stuff tends to age, so after a year or two (being kept in a cool dry place) tends to set too fast to make jointing large areas quite difficult.

Ok, so you've talked me into buying the proper stuff. I guess if it is much easier to sand than alternatives, it's worth it just for that. I've just had another look at my glass fibre tape and it is much thinner than I remembered, so I am happy to use that after all.

Where did you get these prices? Wickes is much dearer than that!

I had a look on the B&Q web site. it didn't find anything for "jointing" but that's because they call it "joint filler". Since the B&Q tubs are smaller, and that's all Ii need, I'll probably buy one of those. I can't find any British Gypsum products though.

Thanks.

To skim over, you need a paper face, which is on the floor stuck to the back of the wallpaper and all you are left with is a crumbling chalky substance which can't be plastered over.